molding and casting 101

[bill w]

Hello to everyone, I'm a new guy here, my name is bill. I had to adjust some suspension parts on my Camaro (lower A frame), so I thought I'd give a tutorial on molding and casting.

The fist pics are the tools I use, spreading pliers and surgical blade. The parts I will be molding and casting are lower A frame and sway-bar links. In the third pic the gates

and vents are glued to the parts. The A frames have one gate and one vent, they will be gravity poured. The links have a gate will be vacuum filled.

http://images12.fotki.com/v197/photos/0/1629610/8690504/suspension023-vi.jpg

http://images45.fotki.com/v1425/photos/0/1629610/8690504/suspension-vi.jpg

http://images17.fotki.com/v297/photos/0/1629610/8690504/suspension001-vi.jpg

The next few pics show the mold box and mounting the parts. I use 1/4" foam core board to make the mold boxes. I make the box 3/4" larger than the part on all four sides. I mount

the parts on the floor of the box and measure the sides, in this case the box will be 3 3/8" long x 3" wide x 3" high. Add it up and you get a piece of foam core 3" x 12 3/4" + a 1/2"

overlap at the end. I score the panels on one side according to the sizes and fold to make a box with 1/2" extra on the last panel. I then close the box and hot glue the lengths on

all four corners for extra strength. Last I hot glue the box to the floor with parts already mounted.

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-004.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-002.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-006.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-007.html

In the next few pics I mix the RTV. I use a platinum base clear RTV. It's easy to see the parts for cutting open the molds. The formula for figuring the amount of RTV is

length x width x height ÷ 16 x .625. Here we go, 3 3/8" x 3"= 10.125 x 3"= 30.375 ÷ 16= 1.898 x .625 = 1.186 lbs. To convert .186 to oz. multiply .186 x 16 = 2.976oz. I round up to

3oz. so we have 1lb. 3oz. Normally you would figure the area of the part and subtract from your RTV total, but the parts here are small and the RTV saved would be minimal. I make my boxes 1/2"

taller and make a pencil line for a fill mark, which is 3". I vacuum the RTV to eliminate bubbles. The bubbles you see in the mold just poured are caused by the pour and are minimal, they

rise to the top and disappear.

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-008.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-010.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-011.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-032.html

Here the molds are cured for 24hrs., taken out of the box, cleaned and cut open. I wiggle the knife wile cutting to get a scalloped cut, this keeps the halves from sliding and helps with

registration when closing the mold for casting. The last pic shows 0090 x 5/16" bolts with the heads cut off.

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-019.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-020.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-022.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-012.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-014.htm

The next pics show the threaded inserts in the mold. The molds are taped shut with 2" packing tape, funnels made with paper (card stock). The large mold is gravity poured and the small one

is vacuumed in a vacuum chamber, the air is pulled out and when the valve is opened in the chamber it sucks the resin into the mold cavity. The last pic shows the molds filled and ready for

the pressure pot. Casting under pressure gets rid of any air bubbles in the part. I added another mold I did earlier, rubber bushings for the sway-bar links.

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-015.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-016.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-017.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-018.html

The last group shows the molds open, parts taken out and sprue's and vents cut off. I hope this helps some. If there are any questions just ask and I'll try to answer them.

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-025.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-026.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-028.html

http://public.fotki.com/bills69camaro/mold-making-and-casting/suspension-030.html

Edited May 4, 2010 by bill w

[Harry P.]

Nice!

But one suggestion: Post the actual photos here, not just a link to them.

[bill w]

OK what do I do?

Bill

[Foxer]

I clicked the image link for your first photo then right-click on image and chose "copy image location"

Come back to your page and edit your post. Click the Insert Image box above the edit box. Paste that link (ctrl+V) into the box and click Insert Image. The links you posted are links to the html page and won't work pasting them here. The above methot loads the image here from your Foki page.

This looks like a great tutorial. Will be nice if we don't have to jump back and forth and can see the photos on the same page as the text.

Edited May 2, 2010 by Foxer

[Casey]

That's an intersting way of eliminating the need for casting multi-part molds, but with a plastic master, you must be incredibly careful when cutting the molds into sections and freeing the masters.

The clear rubber for the molds is a great idea. Why didn't I think of that?

[bill w]

I clicked the edit but nothing happened.

[amani]

I clicked the edit but nothing happened.

how do you create vacuum for small parts, can you show us the set up?

thanks

[bill w]

Hi Amani, here's my set up for a vacuum chamber.

The vacuum chamber is a 60 qt. cooking pot I bought from a restaurant supply, it's 1/4" thick aluminum. The top is 1" thick plexiglass, I got a 2 ft. square and cut it round on a band saw

to fit the pot. I also made a seal from RTV rubber for an air tight seal. Lastly the pump, it's a 7 cfm, you can get them from a industrial supply. I have about $800.00 invested in this setup, You can get a smaller pot and pump, the price would be lower. That's pretty much it. Hope this helps some. If you have any questions let me know?

Bill

Hosted on Fotki

[Foxer]

I clicked the edit but nothing happened.

I never heard of the EDIT on a post not working. That's one for Harry or Gregg.

[amani]

Hi Amani, here's my set up for a vacuum chamber.

The vacuum chamber is a 60 qt. cooking pot I bought from a restaurant supply, it's 1/4" thick aluminum. The top is 1" thick plexiglass, I got a 2 ft. square and cut it round on a band saw

to fit the pot. I also made a seal from RTV rubber for an air tight seal. Lastly the pump, it's a 7 cfm, you can get them from a industrial supply. I have about $800.00 invested in this setup, You can get a smaller pot and pump, the price would be lower. That's pretty much it. Hope this helps some. If you have any questions let me know?

Bill

Hosted on Fotki

but then how do you apply the vacuum on the mold though? do you attach a tubing to the the spigot of the metal pot, and then attach the other end of tubing to the mold to create vacuum so the casting material flow through? one more question, where do you buy the clear RTV, if you can provide a picture of the container and the price will be great. I hope I didn't ask for too much. Thanks